1. Field of the Invention
This invention relates to liquid flow controls and, more particularly, to a unitary control assembly that selectively a) directs liquid from a supply to a drain and b) filters and directs liquid from the supply to a point of use.
2. Background Art
Devices in many diverse fields require the delivery thereto of metered amounts of water from a supply. One exemplary device is a humidified food treatment cabinet, such as that shown in U.S. Pat. No. 4,835,368, the subject matter of which was co-invented by two of the inventors herein.
The food treatment cabinet in U.S. Pat. 4,835,368 has a reservoir 72 with a heated bottom wall 74 against which metered amounts of water are pulsed at controlled time intervals to produce a desired humidity content within the food treatment/holding space 12 bounded by the cabinet.
To produce a consistent and predictable environment within the cabinet, it is important that the same amount of water be delivered by each pulse against the heated wall 74. This may not occur if there are impurities or debris in the water supply. Even if the contamination in the water is relatively insignificant, over a substantial time period, there is a cumulative buildup of foreign matter that may restrict conduit openings and thereby alter the liquid flow characteristics.
One solution to the above problem has been to place a fine mesh stainless steel filter at the bottom of liquid supply/reservoir tanks 90. However, cleaning and/or changing of the filter is a relatively difficult operation and thus a nuisance to the operator. Because of the inconvenience, the filters are inevitably left in longer than is practical and resultingly the operation of the device is compromised.
As a result of the inconvenience of the filter and the problem of its frequent clogging, it is not uncommon for users of the device to remove the filter altogether, thereby allowing debris to flow unimpeded through the system.
Another problem with conventional screen filters is that the filters are generally relatively small, increasing the likelihood that they may be lost and/or misplaced.
A still further problem is that a conventional screen filter may shift relative to the opening which it covers, leaving space for foreign matter to migrate through the system. This problem also must be contended with when the filter is cleaned. Upon the filter being removed for cleaning or replacement, foreign matter that is not trapped in the filter can flow freely into the system.
A still further problem with prior art reservoirs is that they generally require entirely separate and thus relatively complicated structures to both drain and deliver liquid from the reservoir to a point of use.